1. Field of the Invention
The invention relates to a vacuum support for a burst protection device of graphite.
2. Description of the Prior Art
For protecting closed spaces such as chemical apparatus against a spontaneous pressure rise within the spaces, the use of burst protection devices or rupture discs is known. They break or burst when the pressure permissible for the vessel or apparatus is exceeded and relieve the pressure in the vessel in a very short time. A particularly advantageous material for burst protection devices is graphite which has excellent corrosion resistance and fatigue strength. Furthermore, the graphite is independent of the application temperature in the temperat ure range common in chemical apparatus. A further advantage of burst protection devices of graphite is its brittle fracture nature which results in release of the entire pipe or nozzle cross section suddenly and without delay. If underpressure prevails continuously or temporarily at least in the vessels to be protected, it is necessary or advisable to use special vacuum supports which rest against the surface of the burst protection device facing the vessel and prevent deflection thereof in the direction toward the vessel.
Vacuum supports consist of graphite discs which are provided with a multiplicity of parallel holes. The vacuum supports are generally clamped in such a manner that they are not destroyed if the rupture disc responds and can be re-used. The material-saving mechanical design, on the other hand, reduces the free discharge cross section and the outflow number .alpha. which is defined as the ratio of the effective outflow to the flow in a smooth pipe by an average of about 40%, so that the cross section of the burst protection device must as a rule be increased relative to designs without vacuum support. The other alternative, the simultaneous destruction of vacuum support and burst protection device, is not satisfactory because of the large expenditure of technical means.